The integumentary device is one organ system consisting the the skin, hair, nails, and exocrine glands. The skin is only a few millimeters thick however is by much the largest organ in the body. The mean person’s skin weighs 10 pounds and has a surface area of nearly 20 square feet. Skin forms the body’s external covering and forms a barrier to defend the body from chemicals, disease, UV light, and also physical damage. Hair and nails extend from the skin come reinforce the skin and also protect it from environmental proceed Scrolling come Read much more Below...

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continued From Above... damage. The exocrine glands that the integumentary system create sweat, oil, and also wax to cool, protect, and moisturize the skin’s surface.

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Anatomy of the Integumentary System

Epidermis

The epidermis is the many superficial layer of the skin that covers practically the whole body surface. The epidermis rests upon and protects the deeper and thicker dermis great of the skin. Structurally, the epidermis is only about a tenth the a millimeter thick yet is make of 40 come 50 rows of stack squamous epithelial cells. The epidermis is one avascular region of the body, an interpretation that that does not contain any blood or blood vessels. The cells of the epidermis receive every one of their nutrients via diffusion that fluids native the dermis.

The epidermis is do of several specialized types the cells. Almost 90% that the epidermis is made of cells well-known as keratinocytes. Keratinocytes develop from stem cells at the basic of the epidermis and begin come produce and also store the protein keratin. Keratin provides the keratinocytes very tough, scaly and water-resistant. At about 8% the epidermal cells, melanocytes form the 2nd most plenty of cell form in the epidermis. Melanocytes develop the colours melanin to protect the skin native ultraviolet radiation and sunburn. Langerhans cells space the third most usual cells in the epidermis and make up just over 1% of every epidermal cells. Langerhans cells’ function is to detect and fight pathogens the attempt to go into the body v the skin. Finally, Merkel cells comprise less 보다 1% of every epidermal cells however have the important duty of sensing touch. Merkel cells kind a disk along the deepest edge of the epidermis wherein they connect to nerve endings in the dermis to feeling light touch.

In most of the body, the epidermis is arranged into 4 distinct layers. In the palmar surface ar of the hands and plantar surface ar of the feet, the skin is thicker than in the rest of the body and also there is a 5th layer of epidermis. The deepest region of the epidermis is the stratum basale, which consists of the stem cells that reproduce to kind all that the other cells that the epidermis. The cells of the stratum basale incorporate cuboidal keratinocytes, melanocytes, and also Merkel cells. Superficial come stratum basale is the stratum spinosum layer wherein Langerhans cells space found in addition to many rows that spiny keratinocytes. The spines uncovered here are cellular projections dubbed desmosomes that kind between keratinocytes to host them together and also resist friction. Just superficial come the stratum spinosum is the stratum granulosum, wherein keratinocytes start to develop waxy lamellar granules to waterproof the skin. The keratinocytes in the stratum granulosum space so much removed from the dermis the they start to dice from absence of nutrients. In the special skin that the hands and feet, there is a great of skin superficial come the stratum granulosum recognized as the stratum lucidum. The stratum lucidum is make of number of rows the clear, dead keratinocytes that protect the underlying layers. The outermost layer of skin is the stratum corneum. The stratum corneum is make of numerous rows of flattened, dead keratinocytes that protect the basic layers. Dead keratinocytes are constantly being shed from the surface of the stratum corneum and being replaced by cells showing up from the depths layers.

Dermis

The dermis is the deep class of the skin uncovered under the epidermis. The dermis is mainly made of thick irregular connective tissue together with nervous tissue, blood, and blood vessels. The dermis is lot thicker than the epidermis and also gives the skin the strength and also elasticity. In ~ the dermis there room two distinctive regions: the papillary layer and the reticular layer.

The papillary class is the superficial class of the dermis that borders on the epidermis. The papillary layer includes many finger-like extensions dubbed dermal papillae the protrude superficially towards the epidermis. The dermal papillae rise the surface area of the dermis and contain plenty of nerves and blood vessels that space projected toward the surface ar of the skin. Blood flowing through the dermal papillae administer nutrients and also oxygen because that the cell of the epidermis. The nerves that the dermal papillae are provided to feel touch, pain, and temperature through the cell of the epidermis.

The deeper class of the dermis, the reticular layer, is the thicker and tougher part of the dermis. The reticular layer is do of dense irregular connective tissue that consists of many tough collagen and also stretchy elastin fibers to run in all directions to carry out strength and elasticity to the skin. The reticular layer additionally contains blood vessels to support the skin cells and also nerve organization to sense pressure and pain in the skin.

Hypodermis

Deep come the dermis is a great of loosened connective tissues well-known as the hypodermis, subcutis, or subcutaneous tissue. The hypodermis serves as the versatile connection between the skin and also the basic muscles and bones as well as a fat storage area. Areolar connective tissue in the hypodermis includes elastin and collagen fibers loosely arranged to allow the skin come stretch and move individually of its basic structures. Fat adipose organization in the hypodermis stores energy in the form of triglycerides. Adipose also helps come insulate the human body by trapping human body heat created by the basic muscles.

Hair

Hair is an accessory body organ of the skin make of columns the tightly pack dead keratinocytes discovered in many regions the the body. The couple of hairless parts of the body encompass the palmar surface ar of the hands, plantar surface of the feet, lips, labia minora, and also glans penis. Hair helps to safeguard the human body from UV radiation by preventing sunlight indigenous striking the skin. Hair additionally insulates the human body by trapping heat air approximately the skin.

The framework of hair can be damaged down into 3 significant parts: the follicle, root, and shaft. The hair follicle is a depression of epidermal cells deep right into the dermis. Stem cells in the follicle blee to form the keratinocytes that eventually type the hair while melanocytes create pigment that offers the hair that color. In ~ the follicle is the hair root, the portion of the hair listed below the skin’s surface. Together the follicle produces new hair, the cells in the root push up come the surface until they leave the skin. The hair shaft consists of the part of the hair that is uncovered outside the the skin.

The hair shaft and also root space made of 3 distinctive layers of cells: the cuticle, cortex, and also medulla. The cuticle is the outermost layer make of keratinocytes. The keratinocytes the the cuticle are stacked on peak of each various other like shingles so the the outer tip of each cell points away from the body. Under the cuticle room the cell of the cortex that type the majority of the hair’s width. The spindle-shaped and tightly pack cortex cell contain pigments that give the hair that color. The innermost layer of the hair, the medulla, is not present in all hairs. As soon as present, the medulla usually consists of highly pigmented cells complete of keratin. When the medulla is absent, the cortex continues through the center of the hair.

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Nails

Nails room accessory guts of the skin made of sheets that hardened keratinocytes and found on the distal end of the fingers and also toes. Fingernails and toenails reinforce and also protect the finish of the digits and are provided for scraping and manipulating small objects. There room 3 main parts that a nail: the root, body, and free edge. The nail root is the portion of the nail found under the surface ar of the skin. The nail body is the visible external portion of the nail. The free edge is the distal end section of the nail that has grown beyond the end of the finger or toe.

Nails prosper from a deep layer of epidermal tissue recognized as the nail matrix, which surrounding the nail root. The stem cell of the pond matrix reproduce to type keratinocytes, i m sorry in turn create keratin protein and pack into hard sheets the hardened cells. The sheets that keratinocytes kind the tough nail source that slowly grows the end of the skin and forms the pond body together it reaches the skin’s surface. The cells of the pond root and nail human body are thrust toward the distal end of the finger or toe by brand-new cells being created in the nail matrix. Under the nail body is a great of epidermis and dermis known as the pond bed. The pond bed is pink in color due to the existence of capillaries that support the cells of the pond body. The proximal finish of the nail near the root forms a whitish crescent shape recognized as the lunula wherein a little amount of pond matrix is visible with the pond body. Approximately the proximal and lateral edge of the pond is the eponychium, a class of epithelium that overlaps and covers the leaf of the nail body. The eponychium help to seal the edges of the pond to avoid infection of the basic tissues.

Sudoriferous Glands

Sudoriferous glands room exocrine glands discovered in the dermis of the skin and also commonly recognized as sweat glands. There are 2 significant types the sudoriferous glands: eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands are found in practically every an ar of the skin and also produce a secretion of water and sodium chloride. Eccrine sweat is yielded via a duct to the surface of the skin and is used to lower the body’s temperature v evaporative cooling.

Apocrine sweat glands are discovered in greatly in the axillary and also pubic regions of the body. The ducts that apocrine sweat glands extend into the follicles of hair so that the sweat produced by these glands exits the body follow me the surface of the hair shaft. Apocrine sweat glands space inactive until puberty, at which suggest they produce a thick, oily liquid that is consumed by bacteria living on the skin. The digestion of apocrine sweat through bacteria produces human body odor.

Sebaceous Glands

Sebaceous glands space exocrine glands uncovered in the dermis the the skin that produce an oily secretion known as sebum. Sebaceous glands are uncovered in every part of the skin other than for the special skin the the palms the the hands and soles the the feet. Sebum is created in the sebaceous glands and carried through ducts come the surface ar of the skin or come hair follicles. Sebum acts come waterproof and also increase the elasticity the the skin. Sebum additionally lubricates and also protects the cuticles of hairs together they pass v the follicles to the exterior that the body.

Ceruminous Glands

Ceruminous glands room special exocrine glands discovered only in the dermis of the ear canals. Ceruminous glands develop a waxy secretion recognized as cerumen to defend the ear canals and also lubricate the eardrum. Cerumen protects the ears by trapping international material such together dust and also airborne pathogens that enter the ear canal. Cerumen is make continuously and slowly pushes enlarge cerumen external toward the exterior of the ear canal where it drops out of the ear or is manually removed.

Physiology the the Integumentary System

Keratinization

Keratinization, likewise known together cornification, is the procedure of keratin accumulating within keratinocytes. Keratinocytes begin their life together offspring that the stem cells of the stratum basale. Young keratinocytes have actually a cuboidal shape and contain almost no keratin protein in ~ all. Together the stem cells multiply, they push older keratinocytes in the direction of the surface ar of the skin and into the superficial class of the epidermis. By the moment keratinocytes with the stratum spinosum, lock have begun to accumulate a significant amount that keratin and also have end up being harder, flatter, and much more water resistant. As the keratinocytes reach the stratum granulosum, they have come to be much flatter and are almost completely filled through keratin. In ~ this allude the cells space so far removed from the nutrients that diffuse native the blood ship in the dermis the the cell go through the process of apoptosis. Apoptosis is programmed cell fatality where the cell digests its own nucleus and organelles, leaving just a tough, keratin-filled shell behind. Dead keratinocytes moving into the stratum lucidum and also stratum corneum are very flat, hard, and also tightly packed so together to kind a keratin barrier to protect the basic tissues.

Temperature Homeostasis

Being the body’s outermost organ, the skin is maybe to regulate the body temperature by controlling how the human body interacts v its environment. In the situation of the human body entering a state of hyperthermia, the skin is may be to alleviate body temperature v sweating and also vasodilation. Sweat developed by sudoriferous glands it is intended water to the surface of the body wherein it starts to evaporate. The evaporation of sweat absorbs heat and cools the body’s surface. Vasodilation is the procedure through which smooth muscle lining the blood ship in the dermis relax and allow an ext blood to enter the skin. Blood transports heat through the body, pulling heat away from the body’s core and also depositing it in the skin whereby it can radiate the end of the body and also into the exterior environment.

In the instance of the human body entering a state that hypothermia, the skin is able come raise body temperature v the convulsion of arrector chili muscles and also through vasoconstriction. The follicles of hair have small bundles of smooth muscle fastened to your base referred to as arrector pili muscles. The arrector pili form goose bumps by contracting to move the hair follicle and also lifting the hair obelisk upright from the surface of the skin. This movement results in an ext air gift trapped under the hair to insulate the surface ar of the body. Vasoconstriction is the procedure of smooth muscle in the wall surfaces of blood ship in the dermis contracting to alleviate the overwhelming of blood to the skin. Vasoconstriction patent the skin to cool if blood stays in the body’s main point to maintain heat and circulation in the crucial organs.

Vitamin D Synthesis

Vitamin D, an essential vitamin necessary for the absorb of calcium indigenous food, is created by ultraviolet (UV) irradiate striking the skin. The stratum basale and stratum spinosum great of the epidermis contain a sterol molecule well-known as 7-dehydrocholesterol. When UV light current in sunlight or tan bed lights strikes the skin, that penetrates v the outer layers of the epidermis and also strikes some of the molecule of 7-dehydrocholesterol, converting it into vitamin D3. Vitamin D3 is convert in the kidneys right into calcitriol, the active type of vitamin D. Once our skin is not exposed to sufficient amounts of sunlight, us can develop vitamin D deficiency, potentially resulting in serious health and wellness concerns. The capability to stimulate a vitamin D home test and check our own levels thankfully renders it easier to recognize deficiency.

Protection

The skin offers protection come its underlying organization from pathogens, mechanical damage, and also UV light. Pathogens, such together viruses and bacteria, space unable to get in the body through unbroken skin due to the outermost layers of epidermis containing an unending it is provided of tough, dead keratinocytes. This protection explains the necessity of cleaning and also covering cuts and also scrapes through bandages to prevent infection. Boy mechanical damage from turbulent or spicy objects is mostly absorbed by the skin before it can damage the basic tissues. Epidermal cells reproduce continually to conveniently repair any damage to the skin. Melanocytes in the epidermis develop the pigment melanin, i m sorry absorbs UV light before it can pass with the skin. UV light can reason cells to become cancerous if no blocked from entering the body.

Skin Color

Human skin shade is regulated by the interaction of 3 pigments: melanin, carotene, and also hemoglobin. Melanin is a brown or black pigment developed by melanocytes to protect the skin from UV radiation. Melanin offers skin that is tan or brown coloration and provides the shade of brown or black hair. Melanin production rises as the skin is exposed to higher levels the UV light bring about tanning that the skin. Carotene is one more pigment present in the skin the produces a yellow or orange cast to the skin and also is many noticeable in people with short levels that melanin. Hemoglobin is an additional pigment many noticeable in people with small melanin. Hemoglobin is the red pigment discovered in red blood cells, but can be seen v the great of the skin together a irradiate red or pink color. Hemoglobin is most noticeable in skin coloration throughout times that vasodilation as soon as the capillaries that the dermis are open up to carry more blood to the skin’s surface.

Cutaneous Sensation

The skin permits the body to feeling its external environment by choose up signals because that touch, pressure, vibration, temperature, and pain. Merkel disks in the epidermis connect to nerve cells in the dermis to detect shapes and textures the objects contacting the skin. Corpuscles that touch space structures uncovered in the dermal papillae the the dermis that likewise detect touch by objects contacting the skin. Lamellar corpuscles found deep in the dermis feeling pressure and vibration that the skin. Transparent the dermis there space many complimentary nerve endings that are just neurons v their dendrites spread throughout the dermis. Free nerve endings may be perceptible to pain, warmth, or cold. The density of these sensory receptors in the skin varies throughout the body, resulting in some areas of the human body being an ext sensitive come touch, temperature, or pain than other regions.

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Excretion

In enhancement to secreting sweat to cool the body, eccrine sudoriferous glands of the skin additionally excrete waste products out that the body. Sweat developed by eccrine sudoriferous glands normally consists of mostly water with countless electrolytes and a few other map chemicals. The most usual electrolytes found in sweat room sodium and also chloride, but potassium, calcium, and also magnesium ions may be excreted as well. As soon as these electrolytes with high level in the blood, their visibility in sweat also increases, help to mitigate their presence within the body. In enhancement to electrolytes, sweat contains and also helps to excrete little amounts of metabolic waste products such as lactic acid, urea, uric acid, and ammonia. Finally, eccrine sudoriferous glands can assist to excrete alcohol native the body of who who has actually been drinking alcoholic beverages. Alcohol causes vasodilation in the dermis, leading to increased perspiration as more blood get sweat glands. The alcohol in the blood is soaked up by the cell of the sweat glands, leading to it to be excreted along with the other components of sweat.